1. Field of the Invention
The present invention relates to a central processing unit (CPU) cooling structure and, more specifically, to a heat sink fastener, which uses a buffer spring having a double conical spiral spring body instead of a conventional compression spring to prevent vibration during installation.
2. Description of the Related Art
FIG. 6 illustrates a heat sink fastener used in a CPU cooling structure according to the prior art. This design of heat sink fastener is comprised of a locating bolt A, and a compression spring B mounted on the locating bolt A and stopped between the head A1 and barbed tip A2 of the locating bolt A. By means of the barbed tip A2, the locating bolt A is fixedly fastened to one mounting hole C1 of the circuit board C. This structure of heat sink fastener is still not satisfactory in function because of the following drawbacks.
1. The compression spring B vibrates when compressed, resulting in unstable positioning of the locating bolt A.
2. Because the top and bottom ends of the compression spring B are not maintained in horizontal when the compression spring B compressed, it is difficult to keep the compressed compression spring B in position.
3. When the compression spring B compressed, the periphery of the compression spring B may touch the circuit of the circuit board C by accident, thereby causing a short circuit.
The present invention has been accomplished to provide a heat sink fastener, which eliminates the aforesaid drawbacks. The invention uses a buffer spring instead of compression spring. The buffer spring has a top ring defining a top receiving space, a bottom ring defining a bottom receiving space, and a double conical spiral spring body connected between the top ring and the bottom ring and receivable in the top receiving space and the bottom receiving space when compressed. The top ring and the bottom ring are horizontally maintained in parallel, preventing the double conical spiral spring body from bias when compressed. When compressed, the compressed double conical spiral spring body is received within the top receiving space and bottom receiving space, holding the locating bolt stably in position. Further, because the spring body of the buffer spring has a double conical spiral design, it keeps in balance when compressed.